A tidal disruption event in the nearby ultra-luminous infrared galaxy F01004-2237

Abstract

Tidal disruption events (TDEs), in which stars are gravitationally disrupted as they pass close to the supermassive black holes in the centres of galaxies ¹ , are potentially important probes of strong gravity and accretion physics. Most TDEs have been discovered in large-area monitoring surveys of many thousands of galaxies, and a relatively low rate of one event every 10⁴-10⁵ years per galaxy has been deduced ^2-4 . However, given the selection effects inherent in such surveys, considerable uncertainties remain about the conditions that favour TDEs. Here we report the detection of unusually strong and broad helium emission lines following a luminous optical flare in the nucleus of the nearby ultra-luminous infrared galaxy F01004-2237. This particular combination of variabi­lity and post-flare emission line spectrum is unlike any known supernova or active galactic nucleus. The most plausible explanation is a TDE — the first detected in a galaxy with an ongoing massive starburst. The fact that this event has been detected in repeat spectroscopic observations of a sample of 15 ultra-luminous infrared galaxies over a period of just 10 years suggests a much higher rate of TDEs in starburst galaxies than in the general galaxy population.